Page 379 - Engineering Electromagnetics, 8th Edition

CHAPTER 10 Transmission Lines 361

Figure 10.29 See Problem 10.15.

seen by the voltage source-resistor combination; (b) evaluate the power that
is dissipated by the load; (c) evaluate the voltage amplitude that appears
across the load.
10.15 For the transmission line represented in Figure 10.29, find V s,out if f =
(a)60 Hz; (b) 500 kHz.
10.16 A 100- lossless transmission line is connected to a second line of 40-
impedance, whose length is λ/4. The other end of the short line is
terminated by a 25- resistor. A sinusoidal wave (of frequency f )having
50 W average power is incident from the 100- line. (a)Evaluate the input
impedance to the quarter-wave line. (b) Determine the steady-state power
that is dissipated by the resistor. (c)Now suppose that the operating
frequency is lowered to one-half its original value. Determine the new input
impedance, Z , for this case. (d)For the new frequency, calculate the

in
power in watts that returns to the input end of the line after reflection.
10.17 Determine the average power absorbed by each resistor in Figure 10.30.
10.18 The line shown in Figure 10.31 is lossless. Find s on both sections 1 and 2.

10.19 A lossless transmission line is 50 cm in length and operates at a frequency
of 100 MHz. The line parameters are L = 0.2 µH/m and C = 80 pF/m. The
line is terminated in a short circuit at z = 0, and there is a load
Z L = 50 + j20 across the line at location z =−20 cm. What average
power is delivered to Z L if the input voltage is 100 0 V?
◦
10.20 (a) Determine s on the transmission line of Figure 10.32. Note that the
dielectric is air. (b) Find the input impedance. (c)If ωL = 10 , find I s .
(d) What value of L will produce a maximum value for |I s | at ω = 1

Figure 10.30 See Problem 10.17.